<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <title>基准长度</title>
    <style>
        .outer {
            width: 1000px;
            height: 600px;
            background-color: #888;
            margin: 0 auto;
            display: flex;
            flex-wrap: wrap;

            justify-content: flex-start;

          


        }

        .inner {
            width: 200px;
            height: 198px;
            border: 1px solid black;
            background-color: skyblue;
        }

        .inner2{
            /* 设置伸缩项目在主轴上的基准长度，若主轴是横向则宽失效，若主轴是纵向则高失效 */
            /* 默认是auto,原本多宽多高就是多款多高 */
            flex-basis: 300px;
        }
       
    </style>
</head>

<body>
    <div class="outer">
        <div class="inner inner1">1</div>
        <div class="inner inner2">2</div>
        <div class="inner inner3">3</div>

    </div>

</body>

</html>